It doesn't take a visit to the Genius Bar to figure out how Apple became the most valuable company in America.

Its lineup of sleek phones, computers and iPods, irresistible to customers even in tough economic times, propelled it to the No. 1 position by market value Wednesday, surpassing Exxon Mobil. Apple's stock on the open market is now worth more than any other company's.

Apple's stock fell for the day, but Exxon's fell more. Apple finished with a market value of $337 billion, beating Exxon's $331 billion. A single share of Apple stock now costs $363.

Apple occupies a rarefied spot once held by General Electric and Apple's own rival Microsoft. Exxon had held the top spot since 2005.

The power shift is a substantial milestone for Apple, which has enjoyed a triumphant comeback since the 1990s, when it struggled to stay afloat before its co-founder Steve Jobs returned to take the helm.

But it's not just the comeback. Gleacher & Co. analyst Brian Marshall says Apple is giving investors something that has never been seen before. Apple's numbers are huge, with $30 billion in revenue in the latest quarter, for example. Yet Marshall said the 35-year-old company is "growing like a startup."

"Even in 2008 and 2009 Apple grew like a weed and the world was coming to an end," Marshall said.

Apple grew its net income 70 percent to $14 billion and its revenue 52 percent to $65 billion in the fiscal year that ended last September. A year earlier, even as other companies - though not Exxon - were reeling from the economic meltdown, Apple's earnings grew 35 percent and its revenue 14 percent.

Apple wasn't always a tech darling. The company, known as Apple Computer Inc. when it was founded in 1976, was on a steep decline before Jobs returned in 1997.